in Sources/_CollectionsTestSupport/MinimalTypes/_CollectionState.swift [109:124]
func isValidIndex(_ index: MinimalIndex) -> Bool {
if index._state === self { return true }
guard index._state.context == context else { return false }
guard index._offset >= 0 && index._offset <= count else { return false }
switch strategy {
case .allIndices:
guard index._state.id == self.id else { return false }
case .afterChange:
if index._offset < count {
guard index._state.id == indexValidity[index._offset] else { return false }
} else {
guard index._state.id == endIndexValidity else { return false }
}
}
return true
}